Hexamethylene-tetramine thiocyanate has been used for a long time for combatting bacterial infections in veterinary medicine. It has been also known as having high antimycotic activity and being apt for preventing and diminishing yeasts and moulds in animal feed. (See DT-OS No. 22 43 982)
Hexamethylene-tetramine-thiocyanate is formed when concentrated aqueous solutions of hexamethylenetetramine are combined with equimolar amounts of thiocyanic acid. One way of production consists of combining hexamethylenetetramine, ammoniumthiocyanate and hydrochloric acid.
However, thiocyanic acid is not stable in aqueous solution, showing decomposition already at concentrations of 6% and above. Moreover, hexamethylenetetramine-thiocyanate splits off ammonium-ions under the influence of heat in aqueous solution or by influence of high humidity.
In order to overcome these disadvantages, according to DT-PS No. 812 912, hexamethylenetetramine, ammonium-thiocyanate and sulfuric acid are reacted in organic solvents, e.g., methanol or ethanol, whereby a stable mixture of hexamethylenetetramine-thiocyanate and ammoniumsulfate is obtained. The stabilizing influence of ammoniumsulfate can even be observed in aqueous phase (see DT-PS No. 860 052). A stable salt complex of the formula (C.sub.6 H.sub.12 N.sub.4.HSCN).sub.2.(NH.sub.4).sub.2 SO.sub.4 is formed.
A variation of above mentioned process consists, according to DT-PS No. 881 041, in substituting an alkaline earth metal thiocyanate for ammoniumthiocyanate, whereby an insoluble alkaline earth sulfate is obtained and removed from the mixture. The clear filtrate is then stabilized by adding hexamethylene-tetramine, thereby increasing the pH-value, and may be administered directly in this form for injections.
However, utilization of aqueous solutions containing hexamethylene-tetramine-thiocyanate is impaired by the fact, that the product decomposes when evaporized and dried, under formation of ammonium salts. Pure products are obtained only with the aid of alkanoles as precipitating agents at low temperatures.
In practice it has been therefore necessary to isolate hexamethylene-tetramine-thiocyanate as a complex salt, together with ammoniumsulfate or ammoniumphosphate. Products thus obtained are nevertheless not very stable and readily form lumps during storage and exposure to air due to their hygroscopic properties.